A friend put me onto the Unisense E 3rd party sensor package. You can find the details here. If the page loads in German then I've found right click and select translate turns it into English. The package provides height, vario, as well as flight pack volts, amps, wattage, motor rpm. There is an extensive setup possible using a USB connection to a PC once you have downloaded the control programme from the site. The product can be set up in the settings function to operate with a wide range of radio equipment. I use JR DMSS and it works fine for me. Worth a look as it costs Euro 65.90 which would probably only get you one sensor from the JR catalogue!

Their UniLog 2 also works with several brands as well if you want to measure higher currents (up to 400A). With the UniLog, as well as telemetry, you also get more detail at the higher on board logging rate of 20Hz.

While I'm here, here's a typical telemetry screen from the OpenTx system, and yes I use telemetry a lot and find it very useful indeed, especially when a model is new.

Apart from voice call outs of various parameters like LiPo mAh used, battery volts, height etc it will alarm if signal strength is getting low, well before I lose control and likewise, warn if Rx battery is getting low.

If I really want to I can also look at graphs after a flight to see just what went on during the flight. For instance I can check how signal strength went for the whole sortie. This gives me much more confidence in the installation than a range check on the ground can. Or I can check all the individual LiPo cells to check that one wasn't dropping lower than others at any point during it's discharge.